February 21, 2013
01:00 PM (EST)

News Release Number: STScI-2013-07

Stellar Motions in Outer Halo Shed New Light on Milky Way Evolution

February 21, 2013: Peering deep into the vast stellar halo that envelops
our Milky Way galaxy, astronomers using NASA's Hubble
Space Telescope have uncovered tantalizing evidence for
the possible existence of a shell of stars that are a
relic of cannibalism by our Milky Way.

Hubble was used to precisely measure, for the first
time ever, the sideways motions of a small sample of
stars located far from the Milky Way galaxy's center.
Their unusual lateral motion is circumstantial evidence
that the stars may be the remnants of a shredded galaxy
that was gravitationally ripped apart by the Milky Way
billions of years ago. These stars support the idea
that the Milky Way grew, in part, through the accretion of
smaller galaxies.